In today's market, merchants are constantly looking for ways to improve the design of consumer products to render such goods unique and attractive and thereby increase revenue by sale of such products. The market for consumer goods is a competitive one. Colors and image affecting pigments are used to differentiate goods and/or improve the products' aesthetic appeal. As often is the case with plastic articles, color is achieved by incorporating colorants into plastic during molding or other forming processes. In the coloring of molded plastic articles or the incorporation of colorants in coatings, the colorants are often solid inorganic pigments. Pigments used to color goods comprise a vast industry.
Regardless of application or industry, merchants understand the importance of color and image affecting pigments in the sale of goods. Special color effects on articles drive new aesthetic trends, create more dynamic visual impact and improve brand recognition and product differentiation. To achieve color effects, often color effect pigments are employed. Effect pigments, such as pigments that induce iridescence, are used in a range of industries which includes articles such as molded plastics used for automobile or motorcycle finishes/coatings; sporting equipment such as helmets, skates, snowboards, skateboards; solid-surface applications such as kitchen countertops, bath vanities, or flooring including tiles; sanitary wares, such as sink basins, shower stalls or bath tubs; decorative articles, vases, bowls, containers, films, glitter, home sidings, and architectural coatings.
Often consumers make color the key reason for purchasing an article. The importance of color is particularly noticeable in consumers' decision for purchasing cars, home goods, and home appliances. Merchants realize how making available a range of colors or selecting a particular color for a specific good can greatly increase consumer appeal and thus revenue. This is evidenced by the plethora of colors offered for goods such as cars; cycles; household appliances including toasters, blenders, coffee makers; solid surfaces such as floor tiles and kitchen countertops; and in color trends dictated by fashion each season.
Marketing strategies have been developed that use color as a tool in attracting a specific gender to a product or in inviting and not alienating a gender to goods that have traditionally been geared to the opposite gender. For instance, today dark or neutral colors are used to invite males to purchase goods such as home wares, which had traditionally been purchased by females. Similarly, electronic casings such as casings for computers, telephones, portable music devices, digital organizers, etc. have been colored in bright colors to entice females to purchase those products.
The wide range of colors and color effects in the marketplace correlates to the advances in pigment technology. Pigments exist in both natural and synthetic forms. As mentioned above, color effect pigments are one type of pigment presently used to color articles. Normally metal oxides and variations thereof are used to provide these color effects. The color effect pigments are valued for imparting luster or iridescence. For instance, nacreous pigments produce pearl-like, metallic, and iridescent effects. A widely used type of color effect pigment comprises muscovite mica platelets coated with a metallic oxide, such as titanium dioxide. This type of pigment was first described in L. M. Greenstein, “Nacreous (Pearlescent) Pigments and Interference Pigments”, Pigment Handbook, Volume 1, John Wiley & Sons, Inc., pages 829-858 (1988). The unique appearance of effect pigments is the result of multiple reflections and transmissions of light. The platelet substrate usually has a refractive index which is different from the coating and usually also has a degree of transparency. The coating is in the form of one or more thin films which have been deposited on the surfaces of the platelets. One important aspect of the coating on the platelet is that it must be smooth and uniform in order to achieve the optimum pearlescent appearance. The reason is that if an irregular surface is formed, light scattering occurs and the coated platelet will no longer function as an effect pigment. In addition, the coating should adhere strongly to the platelet or else the coating will become separated during processing, resulting in considerable breakage and loss of luster.
A relatively thin titanium dioxide coating produces a pearl-like or silvery luster. Mica platelets with thicker coatings produce color, even though the components are colorless, through the phenomenon of light interference. This type of coated platelet is known as an interference pigment. The color, called the reflection color, is seen most effectively by specular or mirror-like reflection, where the angle of reflection equals the angle of incidence. The reflection color is a function of optical thickness, i.e. the geometrical thickness times the refractive index, of the coating. Optical thickness of about 80 nm to about 140 nm produce reflections which may be called white, silvery or pearly while optical thicknesses of about 150 nm or more produce color reflections.
The pigments which are most frequently encountered on a commercial basis are titanium dioxide-coated mica and iron oxide-coated mica pigments. It is also well known that the metal oxide layer can be overcoated to achieve various desired effects. For instance, Linton, U.S. Pat. No. 3,087,828, describes mica coated with various oxides including those of titanium, iron, cobalt and chromium over which, if desired, a layer of calcined titanium dioxide can be positioned. Brand, U.S. Pat. No. 3,711,308, describes mica coated with a first layer which is a mixture of oxides of titanium and one or more metal oxides which can be, for instance, the oxides of iron, chromium and/or cobalt and a second layer of titanium dioxide. Franz, U.S. Pat. No. 4,744,832, describes coating mica with a layer of titanium dioxide and calcining to form two layers, an inner titanium dioxide layer and an outer pseudobrookite layer. A second layer of iron oxide is deposited and the pigment is recalcined.
Effect pigments need not only be mica-based, but may be glass-based or comprise other types of platelets. Commonly assigned U.S. Pat. Nos. 6,794,037; 6,800,125; and 6,821,333 disclose color effect materials. The effect materials are composed of a plurality of encapsulated substrate platelets in which each platelet is encapsulated with a highly reflective layer which acts as a reflector to light directed thereon, a spacer layer which is selectively transparent to light directed thereon, and optionally an iron oxide layer which may either be on the spacer layer or the highly reflective layer when present. Suitable highly light reflective layers may include for example, silver, gold, platinum, palladium, rhodium, ruthenium, osmium, iridium, or an alloy thereof. Suitable spacer pigment layers may include metal oxide, nitride, fluoride or carbide or polymer.
Tamio Noguchi, “Black Iron Oxide Coated Thin Filler Pigment”, IFSCC, Yokohama, pages 618-639 (Oct. 13-16, 1992) and U.S. Pat. No. 4,867,793 teach Fe3O4 coated mica.
Pearlescent pigments containing ferrites are known in the art. For example, U.S. Pat. No. 5,344,488 and DE 4120747 describe the deposition of zinc oxide onto mica platelets which had been coated with iron oxide. It is also well-known that the metal oxide layer may be over-coated. For instance, said U.S. Pat. No. 3,087,828 describes the depositing Fe2O3 onto a TiO2 layer while U.S. Pat. No. 3,711,308 describes a pigment in which there is a mixed layer of titanium and iron oxides on the mica that is overcoated with titanium dioxide and/or zirconium dioxide. See also U.S. Pat. No. 4,435,220.
Engelhard Corporation has been actively involved in the pigment arts. For instance, commonly assigned U.S. Pat. No. 6,139,615, which is Engelhard's Black Olive™ pigment, discloses pearlescent pigments containing ferrites. The '615 pigment is obtained by adding metal ions to a slurry of a hydrous iron compound and platy particles and then co-calcining the metal and hydrous iron oxide. Also, commonly assigned U.S. Pat. No. 6,361,593 discloses lustrous interference pigments with black absorption color. The '593 pigment comprises a mica coated with a first layer having a combination of hydrous titanium, iron and either cobalt or chromium oxides or both, and then coating the first layer with hydrous titanium and/or iron oxides.
The '593 pigment, publicized since 2002, is one example of Engelhard's wide array of pigments which is a black mica-based effect pigment having champagne undertones. The pigment displays shades of brown-black that had once been difficult to achieve with mica-based pigments and thereby produces a black, lustrous, pearlescent finish. The '593 pigment has been used in many diverse applications including molded-in plastic or coatings for electronic equipment, appliances, sporting goods and packaging, specialty decorative coatings and inks, coatings and inks for leather goods, solid-surface applications (i.e., countertops and flooring), automotive coatings, and architectural coatings.
However, in light of the ever-increasing importance of color and color effects to entice consumers, a continuous need exists to meet the full potential of pigment technology. Pigment technology must continue to evolve in light of consumer demand. For instance, consumers and merchants are desirous of products possessing magnetic pigments displaying shades other than brown-black and displaying interference colors. As mentioned earlier, advancements in the pigment technology are important in that goods having better eye-appeal may drive a consumer to purchase an item over less eye-appealing/attractive goods. A clear illustration of consumer demand is seen in the home goods market. Homeowners and homebuilders want quality or the appearance of quality wares when constructing or remodeling a home. Architectural designs using iridescent magnetic pigments may serve quite well when vying for customer dollars.
Thus, it is desirable to create new pigment compositions to produce magnetic pigments that have iridescent properties rather than brown-black properties. It is also desirable to produce designs or color patterns/effects having magnetic and iridescent properties and products possessing such properties to increase the articles' appeal. Equally desirable is a method to color an article with pigments to create new color variations, effects and/or color designs and patterns.